A point charge of mass 0.185 kg, and net charge +0.340hangs at rest at the end of an insulating

A point charge of mass 0.185 kg, and net charge +0.340hangs...

A point charge of mass 0.185 kg, and net charge +0.340$\mu$C hangs at rest at the end of an insulating cord above a large sheet of charge. The horizontal sheet of fixed uniform charge creates a uniform vertical electric field in the vicinity of the point charge. The tension in the cord is measured to be 5.18 N. Calculate the magnitude and direction of the electric field due to the sheet of charge (Fig. 16-67). FIGURE 16-67 Problem 61. (CANT COPY FIGURE)

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00:01 Okay, so for this one, you have a hanging mass, and you know it's between two plates and that those plates are causing an electric field, and we're trying to figure out what that field is, what its magnitude is in which way it's pointing.

00:17 So doing a free body diagram on the charge, we know we have tension up, and then we have weight down.

00:23 These are not drawn to scale, sorry.

00:25 And then we know we have an electric field, but the electric field could point up or it could point down.

00:31 So if it points up, i'm going to count that as positive.

00:33 If it points down, i'll count that as negative.

00:36 And then the force, electric force is this charge magnitude times the electric field.

00:41 So i'm going to go ahead and write down the givens.

00:43 I meant to write that down in the beginning, but i like for the givens to, you know, kind of naturally come into conversation.

00:52 I guess.

00:53 I'm not sure which one's easier.

00:54 But tension 5 .18, mass, 0 .185 kilograms.

01:01 And the charge is 0 .340 times 10 of minus 6.